This invention relates to an improved thermoelectric heat exchanger that provides high efficiency of operation.
Thermoelectric cooling elements have been commercially available for some time. Each element includes a large number of thermocouples which, when powered by a suitable electrical voltage, absorb heat on one surface of the cooling element and transfer it to an opposing surface.
Finned heat sinks are often provided for both surfaces of the thermoelectric cooling elements. In general, it is important to provide good thermal contact between the thermoelectric cooling elements and each of the heat sinks if operating efficiency is to be maximized.
One approach to this problem is that shown in FIGS. 2 and 3 of Katon U.S. Pat. No. 3,229,469. In this system, a common heat sink extends across multiple thermoelectric cooling elements on one side, while the heat sinks on the opposite side of the cooling elements are sized such that each heat sink engages only a single cooling element. This approach has the disadvantage of requiring a large number of heat sinks and suitable mounting devices for each heat sink.
The heat pump shown in Fenton U.S. Pat. No. 4,065,936 utilizes a larger number of thermoelectric cooling elements for each heat sink, but this approach can reduce operating efficiency. In particular, commercially available thermoelectric cooling elements vary in height, and when a large number of cooling elements are sandwiched between two opposed heat sinks, problems can be encountered in obtaining intimate contact between the heat sinks and each of the cooling elements.
Mole U.S. Pat. No. 3,500,650 shows another arrangement in which two pairs of thermoelectric cooling units are provided for each pair of heat exchangers. The disclosed structure connects all of the thermoelectric cooling elements in series, which can result in undesirably high voltage drops across some of the cooling elements and undesirably low voltage drops across others. Such variations in the voltage drops across separate ones of the cooling elements can materially decrease operating efficiency. Similarly, the heat pump shown in Le Couturier U.S. Pat. No. 4,007,061 utilizes a mosaic of thermoelectric elements which are clamped in place between opposed supporting elements. Variations in height between adjacent cooling elements can interfere with efficient thermal conduction between the cooling elements and the heat sinks.
It is an object of the present invention to provide an improved, high efficiency thermoelectric cooling unit which ensures excellent thermal contact between the individual cooling elements and the heat sinks, and which also ensures that the voltage drop across individual ones on the cooling unit elements do not vary excessively.